For anyone interested in the technical aspects of the Rangitira, this comes from The Press, 3 February 1936:CONSTRUCTION OF RANGATIRAFOUR YEARS IN COOK STRAIT SERVICEAN UP-TO-DATE VESSEL
The Union Steam Ship Company's turbo-electric ship Rangatira was, in construction and equipment, the most modern ship in Australia or New Zealand, when she was put into service about four years ago. Her steering and reversing capabilities were found by the builders' tests to be highly satisfactory. She arrived in Lyttelton on November 2, 1931, and entered into the steamer express service on November 3.
She was launched from the yards of Vickers-Armstrong at Barrow-in-Furness on April 16 of the same year, and came to New Zealand through Panama under her own steam. The power output of the Rangatira is approximately one-third of that of Lake Coleridge, and would supply a city of moderate size. She has twin screws, electrically-driven, whereas the Maori and the Wahine are propelled by triple screws, the centre one driven by high-pressure turbines, and those at the side driven by low-pressure turbines.
She is fitted with a bow rudder similar to those on the Wahine and the Maori, a type which has proved successful in expeditious berthing. A comparison between the Rangatira and the Wahine is as follows:-
| Rangatira||420 ft ||60ft 6in||5500|
|Wahine||375 ft||52ft 2in ||4436|
The Rangatira is 400 feet between perpendiculars, and 29 feet in moulded depth from the upper deck. Her loaded draft is 17 feet, approximately the same as the Wahine. There are five decks on the Rangatira, and her hull is subdivided by watertight bulkheads to meet the full requirements of the Board of Trade. Fire screens are fitted on the main upper deck and promenade, and every precaution has been taken to ensure the maximum amount of safety for passengers and crew.Vessel's Accommodation
Accommodation is provided for about 720 first-class passengers, about 600 being accommodated in cabins and the remainder in public rooms; 236 second-class passengers, 170 in cabins and 66 in public rooms; and a crew of 112. Twelve lifeboats, with a capacity of 680, are provided, and there are also rafts on board. The Thermotank system of ventilation is fitted throughout.
Provision is made for carrying a certain amount of cargo, including large spaces for motor-cars in the 'tween decks, where a certain number of horse-stalls are also fitted. Each cargo hold is provided with a hatchway trunked up through the accommodation decks and served by means of two steel derricks and two electric winches. An electric windlass and capstan are fitted forward, and twin electric capstans aft for mooring purposes. Electric hydraulic steering gear, with telemotor control from the bridge, is placed on the lower deck aft, and a bow rudder is fitted forward for manoeuvring purposes, with a similar type of steering gear. Propelling Machinery
The main propelling machinery consists principally of two separate turbo-alternators, each with its own condensing plant and auxiliaries, two double unit synchronous motors which are coupled direct to the twin propeller shafts, a contractor cubicle to control the power from the alternators to the propulsion motors, and two balancer booster sets for excitation purposes.
The ratings for the machines are as follows:—Two 8.T.-H. impulse type turbo-alternator sets, maximum 5120 k.w., 3080 r.p.m., 3150 volts, three-phase; two double-unit synchronous propulsion-motors, each 6500 s.h.p., 220 r.p.m., 3150 volts, three-phase.
For supplying all the auxiliary lighting, and cooking loads, three 8.T.-H. 350 k.w., 220-volt geared combined condenser turbo-generator sets are installed. There are two main condensers of Weir's regenerative type having a total cooling surface of 13,500 square feet, the capacity of the condensers being sufficient to maintain a vacuum of 284 inches of mercury with a sea temperature of 70 degrees F. The steam generating installation consists of six Yarrow high-pressure water-tube boilers of the five-drum, single-flow, front-fired type, fitted with superheaters and tubular air heaters. Steam is generated at 400lb and superheated at 725 degres F. The total generator surface is about 27,600 square feet, and the total superheater surface about 9000 square feet. The total area of the tubular air heaters is about 27,648 square feet, the capacity. The boilers are arranged to burn oil only under the forced draught air-duct system.
Air is supplied to the boilers by six electrically driven fans of Howden's double-inlet type, against a water gauge pressure of six inches. The oil fuel installation comprises two duplex units, electrically driven, one working and one stand-by set, one simplex unit being provided for harbour purposes with a steam-driven pump. The auxiliary machinery was of the latest and most improved type in use when the ship was built.
The Rangatira's speed trials were carried out on the Firth of Clyde. A series of progressive runs was made, some on the Skemorlie measured mile and the remainder on the measured course off Arran Island. The contract required a speed of 22 knots to be obtained with 10 per cent, overload. The trials showed that this speed could be easily achieved, without developing the full overload capacity of the machinery. No difficulty was found in the working of the electrical machinery and the steam plant, notwithstanding the rather high steam pressure and superheat. Fuel consumption trials were also carried out at speeds of about 20,18, and 13 knots, with only one alternator in use at the last two speeds, The machinery proved to be very economical, and ran quietly and without vibration. The reversing and steering capabilities were highly satisfactory. The time required to commence going astern from 20 knots ahead was two minutes 10 seconds, the vessel being stopped in about four ships' lengths.